I don't believe there is anyone out there who just likes to sell. It is an incredibly volatile way to make a consistent living. Specially asking them to believe that only you believe in.

We all know that developer who wanted to start their own startup/product but felt into hard times and so to keep the lights running they started to do consultancy/freelancing on the side. Then consultancy became their main thing and the startup was sent to the back burner or they just quit the venture entirely.